This work reports the measurement of termolecular charge transferreactions of He2+ into nonassociative product channels. In this study ion destruction frequencies have been experimentally determined from the selectively excited fluorescence of N2+ in high pressure afterglows of mixed gases excited by an intense electron beam discharge. Data have been obtained as functions of helium pressure over the range from 300 to 1500 torr and as functions of the partial pressure of reactant from 25 to 400 μ Hg. From these data, pressure‐dependent rate coefficients have been extracted and subsequently resolved into contributions from bimolecular and termolecular components for reactions of He2+ with Ne, Ar, N2, CO, CO2, and CH4. The bimolecular components have been found to agree with the ESSA flowing afterglow results to within experimental error, and in some cases the values reported here represent an improvement in precision. The sensitivity of the method has been sufficient to detect termolecular components as small as 2×10−30 cm6/sec and values were found to range widely from 2×10−30 for Ne to 67×10−30 cm6/sec for CO2. The size of these termolecular rates suggests the general importance of three‐body ion–molecule reactions in higher pressure plasmas such as those found in e‐beam lasers.

The emission from CO2+ produced by collisions of He+, Ne+, Ar+, and Kr+ has been examined under single collision conditions at 0.1 nm spectral resolution using a beam technique with energies from 0.2 to 4 keV. A fine structure is observed that extends through the 300 to 500 nm region. It has been identified as bending transitions in the ? 2Πu→? 2Πg system of CO2+. The bending transitions in this system have not been analyzed previously. Collisions of the inert gas ions with CO2 produce CO2+ (? 2Πu) with extensive bending vibrations excited, while collisions with H2+, electrons and photons produce the ? 2Πu state with no observable bending. For the heavy ion collisions (except H2+) up to six quanta of bending vibrations are excited. The fraction of ? state produced with bending modes excited range from 0.40 to 0.60 of the total Ã state produced in the collisions, depending on velocity and particle identity. To explain these observations we propose formation of a quasimolecule analogous to HCO2 which gives a bent CO2 intermediate that is the source of the bending vibrations in the CO2+ ? state product. The emission spectrum of the isotope13CO2+ is presented for the first time. The 13CO2+ spectrum verifies the vibrational assignment of bands involving the asymmetric stretch and allows identification of a perturbation in the ? 2Πg (100) level as a Fermi resonance. The emission cross sections for several He lines have been measured at 4 keV.

The results of an accurate abinitio study of the electronic structure of NO2 have been applied to an analysis of the two important visible and near infrared absorption systems of this molecule. The long wavelength absorption (λ≳6000 Å) arises from an ? 2B2←? 2A1 transition. A theoreticalabsorptionspectrum that is generated from the C2Vabinitiopotential surfaces of these two states qualitatively reproduces most of the features of an experimental low resolution absorptionspectrum between 9000 and 6000 Å. The (0–0) band of the transition is predicted to be several times less intense than nearby hot bands even at temperatures as low as 300 K. The computed ? 2B2spectroscopic parameters are Te=1.18 eV, Re=1.26 Å, ϑe=102°, ω1=1461 cm−1, ω2=739 cm−1, and μ=0.46 D. There is a marked difference between experimentally determined ? 2B2rotational constants and those deduced from the abinitio equilibrium geometry; this datum adds to the rapidly increasing evidence for strong vibronic coupling of the ? 2B2 state with high vibrational levels of the ground electronic state. The theoreticalspectroscopic parameters of the experimentally better understood ? 2B1 excited state are Te=1.66 eV, Re=1.20 Å, ϑe=180°, ω1=1192 cm−1, 2 ω2=960 cm−1, ω3=2040 cm−1, and μ=0.0 D. The adiabatic excitation energy, bond angle, and bending frequency are in good agreement with experiment. However, the theoretical equilibrium bond length is significantly shorter than the value deduced from the experimental spectroscopic data and possible reasons for this discrepancy are discussed.

Power broadening of the P (18) (100) – (001) vibrational–rotational transition was studied by irradiating low pressure CO2 gas by CO2 laser pulses. The number of molecules excited to the upper level was related to the intensity of the 4.3 μ laser‐induced fluorescence. Under conditions where collision effects may be neglected, the number density of the excited molecules is determined by the intensity of the laser field. The CO2 sample was placed both inside and outside the laser cavity. The excitation to the (001) level was studied by measuring the fluorescence intensity as a function of the laser intensity. The interactions of a molecule with running and standing wave fields are considered theoretically. In the running wave case the Rabi strong‐field solution is integrated over the molecular velocities and orientations with respect to the field polarization. An exact solution for the density matrix in the standing wave case is derived. The total number of molecules excited to the upper level is calculated for both running and standing wave fields and compared to the experimental data. Specific interesting features of the standing wave solution are discussed.

Effective cross sections for excitation of atomic oxygen by 600–3000 eV electrons were obtained for the OII 4351.3 Å spectral line corresponding to the 3p′2D5/20 →3s′2D5/2 transition and the OII 4414.9 Å and OII 4417.0 Å lines of the 3p2D0→3s2P multiplet. Oxygen atoms were produced in the absence of O2 molecules by the N+NO→N2+O titration reaction. To minimize O atom recombination and elasticscattering of the electron beam, the N2–O gas mixture was expanded into a vacuum chamber resulting in a free jet flow. This provides a unique technique for excitation cross section measurements of free radicals and reactive gases.

A simple threshold photoelectron energy selector was installed in the source of a conventional photoionizationmass spectrometer to measurephotoionization thresholds. In this work, HF, DF, and F2 were investigated. A number of vibronic levels of the HF+ and DF+ ions, not observed by HeI photoelectron spectroscopy, have been detected, from which spectroscopic constants of the molecular ions could be inferred for comparison with recent emission spectroscopy data. The threshold photoelectron spectra show some complicated structure associated with resonant autoionization of molecular Rydberg states belonging to series converging to the various vibronic levels of the ions.

Mass spectrometric work was combined with abinitio quantum chemical calculations at the STO‐3G level to examine the stability and structure of the ions Li2Cl+, Li2F+, Na2F+, Na2Cl+. The stability (based on M2X+dissociation) order is Li2F+≳ (Na2F+, Li2Cl+) ≳Na2Cl+ for both theory and experiment. The calculations give all ions in the linear configuration.

We have measured the absolute rate coefficient for collisional deactivation of O(21S) by H2O. The experimental method involved electron‐beam irradiation of mixtures of H2O and O2 in high‐pressure Ar; the irradiationenergy initially deposited in the argon transferred to O2 to produce O(21S) atoms. Observation of the O(21S) lifetime as a function of H2O pressure permitted deduction of a quenching coefficient of 1.27±0.15×10−10 cm3 s−1.

Light absorption techniques are used to study the temporal dependence of the number densities of the 5s′00 and 5s12 krypton metastable atoms during the decay period (afterglow) of a pulsed discharge in krypton and krypton–nitrogen mixtures. The sensitivity of the temporal properties of the 5s′00 state of krypton to discharge pulse conditions was attributed to an electron destruction process. The 5s12 state was not affected by discharge excitation conditions, permitting the measurement of the diffusion coefficient (Dp0=29.3 cm2 sec−1 Torr) and of the two‐body and three‐body reaction rate constants in pure krypton (k1=2.44×10−15 cm3 sec−1 and k2=2.59×10−32 cm6 sec−1, respectively). In krypton–nitrogen mixtures the additional loss of the 5s12 state of krypton due to its reaction with nitrogen was determined to have a reaction rate constant of 3.33×10−12 cm3 sec−1. Light emission studies made using a flowing afterglow system show that this process populated a wide range of vibrational levels of the B3Πg state of the nitrogen molecule.

Ultrasonic wave absorption and velocity data seem to indicate the existence of some type of phase transition in single crystal salts of copperlanthanum nitrate in the neighborhood of 240°K. The nature of the phase transition observed at 240°K could not be explained by this experiment. The absorption coefficient varies linearly with the frequency (10–200 MHz) and shows a temperature dependence of 1/Ta, where a ranged from 1.8 to 3.0 depending on the orientation except the anomaly at 240°K.

The dynamics of intramolecular vibrational energy transfer is studied, with particular reference to its effect on the unimolecular dissociation rates of isolated molecules. The molecule is represented as a set of classical, coupled, nonlinear (anharmonic) oscillators which transfer energy through resonant interactions. We suggest that isolated nonlinear resonances (which predominate at low energies) lead to trapping of the vibrational energy of the system, hence to slow vibrational relaxation, while resonance overlap at higher energies leads to rapid energy exchange and the random lifetime distribution assumed by RRKM theory. Results are presented for some simple model systems, and the approach is compared with other recent theoretical descriptions of vibrational relaxation in isolated molecules.

The nuclear spin–lattice relaxation of carbon‐13 enriched methylene iodide (diiodomethane) dissolved in benzene‐d6 has been studied both with and without proton decoupling and using various pulse techniques to perturb the AX2(13CH2) spin system from thermal equilibrium. The return of the spin system to steady state was monitored using carbon‐13 Fourier transformnuclear magnetic resonance techniques. It is shown that the equation of motion of the spin density matrix reduces in general to the master equation for populations in terms of interlevel transition rates, and that a linear transformation based on the complete set of irreducible spherical tensor operators which span the spin space further simplifies the equation of motion. The relaxation was modeled as intramolecular dipole–dipole interactions modulated by rotational reorientation of the molecule plus other mechanisms which can be treated collectively as external random magnetic fields interacting with the nuclear spins of interest. Extreme narrowing is assumed. The model was parameterized in terms of the spectral densities of fluctuations in the molecular rotational reorientation and in the external random field along with other necessary parameters characterizing the operation of the NMR spectrometer. A best least squares fit of this model to all of the relaxation data was calculated. From the values of the spectral densities thus obtained all of the interlevel transition rates were calculated. Assuming a rotational diffusion model for the molecular rotational reorientation, the following structural and dynamical parameters were calculated from the dipole–dipole spectral densities: &HCH=104°±2°, Dxx/Dzz =0.205±0.0033, and Dyy/Dzz=0.079±0.057, where Dαα, α=x,y,z, are the elements of the diagonalized rotational diffusiontensor.

The infrared double resonance technique has been used to observe V–Venergy transfer from the ν3 mode of SF6 to other vibration–rotation levels lying 1000 cm−1 or more above the ground state. Results obtained with nanosecond time resolution indicate that the major portion of the transfer occurs in the absence of collisions. Relevance to laser induced, isotope selective, collisionless dissociation is discussed.

Methods are presented for facilitating the calculation of even moments 〈R2p〉 of the end to end vector R and for the inference of the probability distribution in the absence of excluded volume effects. The gain in efficiency of moment calculations is several hundredfold for the first 10 moments, 0⩽p⩽10. The proposed inference scheme is similar to the Hermite expansion from a least square standpoint but differs in choice of weight function. Tests on freely rotating chains exhibit quantitatively useful convergence for all R, including chains with too few bonds to permit ring closure.

The sodium‐23 spin–lattice relaxation time (T1) was determined at 10 MHz on Dowex 50W‐X2 ion exchanger resin as a function of the dielectric constant of the solvent. The relaxation time varied from 24.8 msec in distilled water (D=78.5) to values too short to determine in water–ethanol mixtures below a dielectric constant of 35. Similar studies were conducted on 250 mmsodium bisulfite (NaHSO3) in a series of aqueous–nonaqueous mixtures. The results indicate that T1 may be expressed as a function of the macroscopic dielectric constant for any binary solvent system. For systems with a dielectric constant greater than 65 the relationship is given by T1=a exp(bD), where a and b are constants for a particular solvent system.

The rate equations governing the temporal evolution of photon densities and level populations in pulsed F+H2→HF+H chemical lasers are solved for different initial conditions. The rate equations are solved simultaneously for all relevant vibrational–rotational levels and vibrational–rotational P‐branch transitions. Rotational equilibrium is not assumed. Approximate expressions for the detailed state‐to‐state rate constants corresponding to the various energy transfer processes (V–V, V–R,T, R–R,T) coupling the vib–rotational levels are formulated on the basis of experimental data, approximate theories, and qualitative considerations. The main findings are as follows: At low pressures, R–T transfer cannot compete with the stimulated emission, and the laser output largely reflects the nonequilibrium energy distribution in the pumpingreaction. The various transitions reach threshold and decay almost independently and simultaneous lasing on several lines takes place. When a buffer gas is added in excess to the reacting mixture, the enhanced rotational relaxation leads to nearly single‐line operation and to the J shift in lasing. Laser efficiency is higher at high inert gas pressures owing to a better extraction of the internal energy from partially inverted populations. V–V exchange enhances lasing from upper vibrational levels but reduces the total pulse intensity. V–R,T processes reduce the efficiency but do not substantially modify the spectral output distribution. The photon yield ranges between 0.4 and 1.4 photons/HF molecule depending on the initial conditions. Comparison with experimental data, when available, is fair.

A molecular orbital study is made of the binding and structural distortions of ethylene and acetylene adsorbed on Ni (111). The following results emerge from the calculations. Disigma bridging positions are preferred. Two Ni atom clusters are sufficient for determining adsorbate structures which show distortions similar to those in coordination compounds. Acetylene, at monolayer coverage, occupies half the surfacebinding sites while ethylene occupies a quarter of the bridging sites. Acetylene readily dissociates into CH fragments occupying threefold surface indentations. The calculated energy levels for the various modes of adsorption are related to the photoemissionspectra of Eastman and Demuth.

A phenomenological rate process theory is developed for the storage and rapid recombination of atomic hydrogen free radicals in a crystalline molecular hydrogen solid at temperatures in the range 0.1 K≲T≲4 K. It is shown that such a theory can account quantitatively for the recently observed dependence of the storage time on the storage temperature, for the maximum concentration of trapped H atoms, and for the time duration of the energy release in the tritium decay experiments of Webeler. The theory predicts that maximum atomic hydrogen concentrations of the order 1020/cm3 are realizable for storage temperatures in the vicinity of 0.14 K.

The absorptionspectrum of Ar2 has been photographed at a dispersion sufficiently high to allow a rotational analysis of one band system. From the analysis, the vibrational and rotational constants of the five lowest vibrational levels of the ground state have been determined. These spectroscopic data, together with information from long‐range forces and from the second virial coefficient, have been used to calculate the potential curve of the ground state. This calculated curve is compared with other curves which have been proposed.

A systematic treatment of the simple rotation double groups in general (with any order n of the principal axis) is presented. The LCAS simple symmetry spinors of these groups are given in general for any values of the atomic quantum numbers ljm.